Remote lie detection raises ethical issues

It's obvious when Pinocchio's lying. What about more subtle clues? Scientists say they have the basis of a remote lie detector test that monitors someone's sweat, pulse and blood pressure without them knowing. But is it ethical? (Source: iStockphoto)

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A new way to remotely monitor blood pressure, pulse rate and sweating could be used to screen for health signs as well as to administer lie detection tests on people without their knowledge or consent.

While researchers stress their work remains only proof-of-concept, a commercial version using sub-terahertz waves could theoretically help remotely monitor medical patients, evaluate athletic performance, diagnose disease and detect lies.

The key is in the surprising shape of human sweat ducts.

Recent advances in imaging technology reveals that sweat ducts, the tiny tubes that connect sweat glands to the outside of the skin, are helical, or shaped like corkscrews.

When co-author and colleague Professor Yuri Feldman saw these sweat gland images, they reminded him of the helical antennas often used in basic engineering classes.

First, look at the twists

By measuring certain factors like the number of twists, any beginning electrical engineering student can calculate the wavelength of energy the antenna would interact with, say the physicists.

The wavelength of human sweat glands falls in the sub-terahertz, or sub T-ray, range.

Full T-rays have been used in a variety of other applications recently, from uncovering hidden artwork to finding concealed weapons. T-rays, unlike their energetic cousins x-rays, are harmless.

Next, build a machine

By creating a machine that generates and detects sub T-rays, the scientists say they can look at which wavelengths interact with the millions of tiny 'antennas' buried within the body's largest organ, the skin.

While sweating doesn't produce T-rays, sweat production changes the wavelength that is bounced back off the sweat duct antenna.

By measuring these wavelengths, scientists can, in turn, calculate how much and where a person is sweating.

Then, look at the sweat

Different parts of the body sweat depending on the reason. Eating a spicy chilli pepper causes sweat beads to break out on the forehead.

Sunbathing causes sweat glands to be activated on the chest and back.

Various diseases and medical conditions activate other sweat glands, while also changing blood pressure and pulse rate.

Eventually, with the development of an accurate sweat map and other studies, the physicists hope to create a tool that can diagnose diseases based on where a person is sweating.

In later tests the researchers also measured blood pressure and pulse rate remotely, by monitoring the kinds of sweating directly linked to changes in these vital signs.

Remote monitoring

Currently the only way to measure blood pressure is by using an inflatable pressure cuff or a surgically implanted monitor. The only way to measure sweat is through a cumbersome process that uses electrodes on a small portion of skin.

The new method can do both remotely and constantly.

While cautious about the new research, James Wolff, a doctor at Emerson Hospital in Concord, Massachusetts, who was not associated with the study, says "this could open up a whole new area of research".

Because it has never been possible to monitor sweat, pulse and blood pressure remotely, no one has thought about what the technique could be used for, says Wolff.

Sweaty liars

The device could also be used as a remote lie detector, without their knowledge or consent.

When a person lies, it triggers physiological responses: faster pulse, higher blood pressure and increased sweating. A polygraph machine measures these responses, but it has to be physically attached to a person.

Trained professionals can evade polygraphs, but if a person doesn't know they are being constantly tested the new method could be more effective.

Jonathan Marks, a professor of bioethics at Pennsylvania State University, says that lie detection using this method would still have problems with accuracy.

A person already anxious over something else when they are being scanned could trigger a false positive.

"There are concerns about people's privacy," says Marks. "Is there a justification for screening people en masse for physiological data?